1. Field of the Invention
The present invention relates to an IP telephone system, an IP telephone apparatus and a communications method that perform voice communications via an IP network.
2. Description of Related Art
The recent rapid growth of the Internet has drawn attention to an IP telephone system that enables low-cost voice communications with telephone apparatuses at remote places as well as free voice communications between IP telephone apparatuses owned by subscribers. Among such IP telephone systems, there is a proposal for an IP telephone system that allows the transmitting party to specify a screen display or receiving tone on the receiving party's end for the purpose of improving users' convenience (See Prior Art 1).
On the other hand, as an underlying technology, ENUM is emerging as the focus of attention, enabling communications according to users' individual setting by effectively controlling information used for diversified communications tools, including telephones, faxes, cellular phones and electronic emails. ENUM is designed to identify the Internet service with a unique global identification number such as E.164, using the DNS (Domain Name System). Currently, the IETF (Internet Engineering Task force) is seeking to standardize ENUM platforms, where protocol specifications are discussed (See Publication 1).                [Related Art 1] Japanese Laid Open Publication 2003-188992        [Publication 1] Issued by ENUM Trial Japan “ENUM Trial Japan First Report” May, 2004        
However, the above-described conventional IP telephone system can only allow the transmitting party to specify a desired operation performed on the receiving party's end, the operation being such as the screen display or the receiving tone when calls are received. The conventional IP telephone system is not capable of specifying operations according to call recipients' individual setting.
In general, IP telephone apparatuses used in homes or within corporations are shared by a plurality of users. Among them can be hearing-impaired elderly people who need a volume adjustment. Those users who need such a volume adjustment need to adjust the volume after voice communications start. When users who do not need the volume adjustment are set to talk next, they need to readjust the volume. In such a phone system, users' convenience can be improved when talk volume can be specified upon receiving a call to meet the need of each call recipient.